Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C13/00—Fibre or filament compositions
  • C03C13/04—Fibre optics, e.g. core and clad fibre compositions
  • C03C13/045—Silica-containing oxide glass compositions
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/012—Manufacture of preforms for drawing fibres or filaments
  • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
  • C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma- or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
  • C03B37/01807—Reactant delivery systems, e.g. reactant deposition burners
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
  • C03B2201/12—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with fluorine
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
  • C03B2201/14—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with boron and fluorine
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
  • C03B2201/31—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with germanium
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
  • C03B2201/34—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with rare earth metals, i.e. with Sc, Y or lanthanides, e.g. for laser-amplifiers
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
  • C03B2201/40—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S65/00—Glass manufacturing
  • Y10S65/15—Nonoxygen containing chalogenides
  • Y10S65/16—Optical filament or fiber treatment with fluorine or incorporating fluorine in final product

Definitions

• the present invention relates to a method for producing glass with a predetermined refractive index profile in the form of a gradient profile according to the preamble of patent claim 1.
• a method of the type mentioned is known from DE-A-26 27 821.
• the parabolic gradient profile is generated in a cover layer by doping with fluorine, which is gradually changed in accordance with the gradient profile.
• One of the main goals of optical fibers for optical communications technology is to achieve the lowest possible attenuation and pulse broadening.
• a good homogeneity of the glass is a prerequisite for low attenuation and low pulse broadening can be achieved by giving the fiber core in which the light is guided a certain radial refractive index profile.
• An essentially parabolic profile is suitable for this. With this profile, it is possible to largely compensate for transit time differences between individual mode groups in multimode glass fibers, thereby keeping pulse broadening low.
• the refractive index profile must be adhered to very precisely.
• Glass fibers with a desired refractive index profile in the core area can be produced by first producing a glass rod with a refractive index profile that corresponds to the fiber, and by pulling the fiber from this rod, the shape of the refractive index profile in the The rod remains in the drawn fiber.
• Glass rods with such a refractive index profile for example a parabolic refractive index profile, can be produced using a known CVD method in which glass layers are deposited on the inner wall of a tube and the internally coated tube is shaped into a rod from which the desired fiber can be drawn that a large number of layers of glass with slightly different refractive indices are melted.
• a reaction gas mixture is passed through the externally heated tube.
• the chemical reaction is thermally triggered in the heating zone inside, resulting in a powder having the composition of a glass, which is deposited on the inner wall of the tube and which is melted clear in the heating zone to form a glass film.
• the refractive index of the deposited glass can be influenced via the composition of the reaction gas mixture.
• the object of the invention is to provide a method for producing glass with a predetermined refractive index profile in the form of a gradient profile, in which the refractive index profile produced is free from undesirable refractive index fluctuations.
• each of the layers which determine the gradient profile together is doped with fluorine and with at least one other dopant, and that only the doping with the other dopant changes , the doping with fluorine is kept constant for all layers.
• the glass layers are deposited in the form of layers of alkali-free quartz glass which are doped with fluorine and with one or more other dopants.
• the deposited quartz glass layers are only doped with germanium and fluorine.
• one or each deposited quartz glass layer is doped with germanium, aluminum, titanium, tantalum, tin, niobium, zirconium, Yb, La, Pb and / or Lb and with fluorine .
• reaction gas mixture which contains a fluorine-containing molecular gas and another dopant, another molecular gas, the concentration of another molecular gas or the mixing ratio or the composition of the further molecular gases being changed in layers.
• a fluorine-containing molecular gas is a gas or gas mixture which, apart from fluorine, only contains elements which themselves or their oxides have no significant tendency to dissolve in glass.
• a fluorine-containing molecular gas which has one or more sulfur fluorine compounds, fluorocarbons and / or nitrogen fluorine compounds has proven to be particularly suitable.
• the fluorine-containing molecular gas according to claim 8 may contain one or more sulfur fluorides, nitrogen fluorides, fluorohalohydrocarbons and / or carbonyl fluoride, all sulfur and nitrogen fluorides and fluorohalogen hydrocarbons being suitable.
• sulfur hexafluoride has proven to be particularly advantageous as a fluorine-containing molecular gas.
• a fluorine-containing molecular gas can also be a gas or gas mixture which, in addition to fluorine, also contains an element whose oxide is readily soluble in glass.
• Such a gas or gas mixture are silicon tetrafluoride, boron trifluoride and / or phosphorus pentafluoride. These gases or gas mixtures can lead to Si0 2 , B 2 0 3 and P 2 0 5 doping.
• the fluorine acts as an oxygen substituent and is present as fluoride bonded to the substance or one or more of the two substances.
• the deposition of the glass layers is carried out by a method according to the combination of claims 1, 3, 5 and 9.
• a quartz glass tube about 1 m long and 20 mm in diameter with a wax thickness of 1.5 mm is heated in a glass lathe with the help of a narrow oxyhydrogen burner.
• First the pipe is cleaned.
• a gas stream consisting of 1100 Nml / min oxygen and 15 Nml / min sulfur hexafluoride is passed through the pipe (N means the reference to normal conditions at 1 bar below 0 ° C).
• the cleaning effect is caused by the sulfur hexafluoride, which has a caustic effect on the glass in the hot zone.
• the burner is moved along the tube at a speed of 15 cm / min in the direction of the gas flow and drives the reaction products formed during the etching.
• the deposition of glass layers that are intended for the cladding of the glass fiber is started. For this, 90 Nml / min silicon tetrachloride are added to the gas flow.
• the SF 6 supply can now be interrupted, but it can also be maintained, but at a reduced value, for example 6 Nml / min.
• a quartz glass powder is deposited in front of the burner, which is doped with fluorine and which is melted clear by the advancing burner to the glass.
• the formation of cladding glass is complete and GeCI 4 gas and, if not already present, sulfur hexafluoride, preferably 6 Nml / min, are added to the gas stream and the GeC1 4 gas stream is passed from burner run to burner run and thus from layer to shift increased by about 44/60 Nml / min.
• the chloride supply is interrupted and the sulfur hexafluoride flow is reduced to about 1.5 1.5 Nml / min and the burner speed is slowed down, so that the tube temperature rises to about 2000 ° C. At this temperature the pipe begins to collapse. Due to the low sulfur hexafluoride flow, the inner wall of the pipe is slightly etched and thus cleaned.
• the rod produced in this way has an outer diameter of 1 mm.
• the diameter of the core is 5.2 mm.
• the germanium concentration increases radially from the outside inwards from 0 to 12% by weight.
• the concentration curve clings closely to a paraboloid with a quadratic parabola as an envelope.
• the fluoride concentration is uniformly approximately 0.6% by weight in all the deposited layers.
• the Ge0 2 concentration sink in the center of the core is extremely narrow with a half-width of only 60 ⁇ m. This is essentially achieved by the cleaning effect caused by the sulfur hexafluoride flow during the collapse process. Rinsing the glass wall with sulfur hexafluoride also leads to a cleaning effect that has an extremely favorable effect on the glass to be produced.
• a Ge0 2 profile Under otherwise identical test conditions, but without the addition of fluorine to the gas phase, a Ge0 2 profile has pronounced peaks and a broad concentration depression in the center of the core. Peaks and valleys fluctuations of approximately 15% were observed. Pulse widths of about 2 ns were observed on a two-kilometer-long fiber from such a preform with pronounced tips. In contrast, a pulse broadening of only 0.5 ns was observed for the same fiber with added fluoride, which corresponds to a bandwidth of 2 GHz / km. Typical attenuation values of the fluorine-doped fiber are 0.8 dB / km at 1.55 / ⁇ m. At 1.39 / ⁇ m 5.5 dB / km (water maximum) were measured. Without the addition of fluorine, the water maximum is higher.
• fluorine doping also has similarly favorable effects with impurities other than Ge, ie Ge0 2 .
• impurities other than Ge ie Ge0 2 .
• the fluorine-containing molecular gases are primarily gases which, apart from fluorine, only contain elements which or their oxides have no substantial tendency to dissolve in the glass used, here SiO 2 .
• these are, in particular, fluorocarbons and fluorohydrocarbons, such as, for example, CC1 2 F 2 and nitrogen trifluoride (NF 3 ) and carbonyl fluoride (COF Z ).
• fluorides of elements can also be used. whose oxides are readily soluble in the glass, here quartz glass. SiF 4 , BF 3 and PF 5 are particularly suitable for this. These substances lead to SiO 2 , B 2 0 3 and P205 doping.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Optics & Photonics (AREA)
• Physics & Mathematics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Glass Compositions (AREA)
• Manufacture, Treatment Of Glass Fibers (AREA)
• Glass Melting And Manufacturing (AREA)

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• 1980
  • 1980-08-18 DE DE19803031147 patent/DE3031147A1/de not_active Ceased
• 1981
  • 1981-08-14 AT AT81106340T patent/ATE23324T1/de not_active IP Right Cessation
  • 1981-08-14 EP EP81106340A patent/EP0046281B1/de not_active Expired
  • 1981-08-17 CA CA000384032A patent/CA1162948A/en not_active Expired
  • 1981-08-18 JP JP56129301A patent/JPS5771832A/ja active Granted
• 1983
  • 1983-03-18 US US06/476,571 patent/US4557561A/en not_active Expired - Lifetime

Patent Citations (1)

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